Manchester Memoirs, Vol. xlvi. (1902), No. 10. 29 



Even in those cases where bodies apparently move by 

 impulse, as in the collision of elastic bodies, the principle of 

 spontaneous motion may not be altogether excluded, for 

 the reason that the motion of a body, after impulse, is the 

 same as that of a body moving by volition. This is well 

 exemplified in the case of a cyclist who, when riding on a 

 machine, moves by volition, but when losing control of 

 it, moves by impulse, and again moves by volition on 

 regaining control of the machine. 



The demonstration which I have given of the 

 spontaneous motion of endothermic compounds clearly 

 shows that volition can no longer be held to be the 

 exclusive attribute of the organised forms of hydro-carbon 

 compounds. Nor can the same attribute be excluded 

 from the beautiful crystalline bodies (as seen in nature 

 and in the laboratory of the chemist) which they possess 

 in common with the higher and the lower forms of 

 organic life. 



Just as the spasmodic and capricious movements of 

 the organised forms of the hydro-carbon compounds 

 create in the mind the idea of spontaneous motion, acting 

 from within, so the regular and rhythmical motions of 

 inorganic substances, under constant conditions, induce, 

 in the earlier stage of man's intellectual development, the 

 idea that such bodies only move by impulse, acting from 

 without, and of necessity. 



Recapitulation. — It has been shown (i) that the 

 geocentric systems of Ptolemy and the older cosmogonists 

 were founded on the simian idea of the immobility of the 

 earth and the diurnal rotation of the celestial bodies. (2) 

 That a comparatively small number of the world's 

 population accept the heliocentric system of planetary 

 bodies from an actual perception of its truth. (3) That 



